<b>HRAC Group 22</b> <font size='2'> (Legacy D) </font> resistant Solanum americanum from United States, Florida

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 22 (LEGACY D) RESISTANT AMERICAN BLACK NIGHTSHADE
(Solanum americanum)

PS I Electron Diversion HRAC Group 22 (Legacy D)

United States, Florida

INTRODUCTION		AMERICAN BLACK NIGHTSHADE
American Black Nightshade (Solanum americanum) is a dicot weed in the Solanaceae family. In Florida this weed first evolved resistance to Group 22 (Legacy D) herbicides in 1985 and infests Tomatoes. Group 22 (Legacy D) herbicides are known as PS I Electron Diversion (PSI Electron Diversion ). Research has shown that these particular biotypes are resistant to paraquat and they may be cross-resistant to other Group 22 (Legacy D) herbicides. The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.

QUIK STATS (last updated Sep 15, 2000 )
Common Name	American Black Nightshade
Species	Solanum americanum
Group	PS I Electron Diversion HRAC Group 22 (Legacy D)
Herbicides	paraquat
Location	United States, Florida
Year	1985
Situation(s)	Tomatoes
Contributors - (Alphabetically)	William Stall
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NOTES ABOUT THIS BIOTYPE

AREAS FOUND

William Stall

Dade, Collier, Manatee, Hillsborough counties.

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GENERAL

William Stall

Publications on mechnism of resistance towards the end of the year.

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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse trials comparing a known susceptible American Black Nightshade biotype with this American Black Nightshade biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.

Genetics

Genetic studies on HRAC Group 22 resistant American Black Nightshade have not been reported to the site. There may be a note below or an article discussing the genetics of this biotype in the Fact Sheets and Other Literature

Mechanism of Resistance

The mechanism of resistance for this biotype is either unknown or has not been entered in the database. If you know anything about the mechanism of resistance for this biotype then please update the database.

Relative Fitness

There is no record of differences in fitness or competitiveness of these resistant biotypes when compared to that of normal susceptible biotypes. If you have any information pertaining to the fitness of Group 22 (Legacy D) resistant American Black Nightshade from Florida please update the database.

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CONTRIBUTING WEED SCIENTISTS

WILLIAM STALL

Professor and Extension Horticulture Specialist Weed Science University Of Florida Horticultural Sciences Department 1590 Long Lake Rd Gainsville, 32611, Florida United States Email William Stall Web : Web Site Link

ACKNOWLEDGEMENTS
The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Florida have been instrumental in providing you this information. Particular thanks is given to William Stall for providing detailed information.

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Herbicide Resistant American Black Nightshade Globally
(Solanum americanum)

Country

FirstYear

Situation

Active Ingredients

Site of Action

New Zealand

2009

Sweet potato

paraquat

PS I Electron Diversion ( HRAC Group 22 (Legacy D)

United States (Florida)

1985

Tomatoes

paraquat

PS I Electron Diversion ( HRAC Group 22 (Legacy D)

Literature about Similar Cases

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Lewthwaite, S. L. ; Triggs, C. M.. 2009. Identification of paraquat-resistant Solanum nigrum and S. americanum biotypes. New Zealand Plant Protection 62 : 349 - 355.

Sweetpotato (Ipomoea batatas (L.) Lam.) plants are highly susceptible to weed competition during their early field establishment period. For a long time, the contact herbicide paraquat has been widely used within the sweetpotato production system, often as the only herbicide applied to control weeds that emerge within the crop. A low rate of paraquat is applied repeatedly over the crop each season, eliminating seedling weeds at a very young stage, until the crop canopy provides adequate competition. However, the application of paraquat to selectively destroy seedling weeds has inadvertently selected for paraquat-resistant weed biotypes. This study confirms growers' field observations that populations of paraquat-resistant solanaceous weeds are now common, identifying them as Solanum nigrum L. and S. americanum Mill. Paraquat cannot be used selectively when these resistant biotypes are present, as the concentrations required to control the weed species would be lethal to the crop itself..

Ferreira, E. A. ; Procópio, S. O. ; Silva, E. A. M. ; Silva, A. A. ; Rufino, R. J. N.. 2002. Anatomical studies of weed leaves. I - Nicandra physaloides, Solanum viarum, Solanum americanum and Raphanus raphanistrum. Planta Daninha 20 : 159 - 167.

This research aimed to study the leaf anatomy of the weed species Nicandra physalodes, Solanum viarum, Solanum americanum and Raphanus raphanistrum to acquire a better understanding of the barriers each species imposes upon herbicide penetration. Completely expanded leaves from the third to the fifth node were collected from plants spontaneously occurring in the field. Three samples, approximately 1 cm², were taken at the central portion of the leaves in each species and used in structural studies, and clarification and observation using a scanning-electron microscope. All species were amphistomatic. The main leaf barrier against herbicide penetration in N. physalodes had high trichome density, whereas in S. viarum, the main barriers had low stomatal density in the adaxial side, high trichome density, high content of epicuticular wax and high cuticle thickness. S. americanum's main leaf barriers had low stomatal density and high cuticle thickness in the adaxial side. High cuticle thickness in the adaxial side was the only barrier observed in leaves of R. raphanistrum..

Chase, C. A. ; Bewick, T. A. ; Shilling, D. G.. 1998. Differential photosynthetic electron transport and oxidative stress in paraquat-resistant and sensitive biotypes of Solanum americanum. Pesticide Biochemistry and Physiology 60 : 83 - 90.

Experiments were conducted to investigate differences in rates of photosynthetic electron transport in paraquat-resistant and -susceptible biotypes of Solanum americanum, and the abilities of resistant and susceptible biotypes to promote oxidative stress. Results indicated that electron transport, measured as photoreduction of ferricyanide by thylakoid membranes, was significantly lower in the resistant biotype, and superoxide production in unilluminated membranes was also lower in this biotype, while oxidative stress following paraquat treatment was greater in the susceptible biotype. It was also found that CO₂ fixation and dry matter accumulation in the intact plant were lower in the resistant biotype. Similar rates of O₂ production were measured in paraquat-treated thylakoids from resistant plants and non-treated thylakoids from susceptible plants..

Chloroplasts and thylakoid membranes were isolated from biotypes of S. americanum (American black nightshade) which are resistant (R) or susceptible (S) to paraquat. Electron transport was measured as photoreduction of ferricyanide to ferrocyanide. The rate of electron transport was greater in the S biotype. Biotype R had a reduced rate of photosynthesis, as measured by CO₂ fixation. Growth course analysis of the biotypes over 4 weeks showed that the S biotype accumulated dry matter most quickly. Superoxide radical production by thylakoids was measured by spectrophotometric determination of ferricytochrome c reduction to ferrocytochrome c by superoxide radicals. In the absence of paraquat, S had a higher rate of superoxide radical production than R, which was enhanced by paraquat. Addition of paraquat to R produced a level of oxidative stress that did not cause irreparable damage. It is concluded that restricted oxidative stress in R is due to reduced electron transport..

Chase, C. A. ; Bewick, T. A. ; Shilling, D. G.. 1998. Characterization of paraquat resistance in Solanum americanum Mill. II. Evidence for a chloroplast mechanism. Pesticide Biochemistry and Physiology 60 : 23 - 30.

Levels of ascorbate and dehydroascorbate, ion leakage and chlorophyll a fluorescence were studied in a paraquat-resistant (R) and paraquat-susceptible (S) biotype of Solanum americanum after treatment with paraquat. A net decrease in total ascorbate was observed in the S biotype over a 3-h period after treatment with paraquat. In the R biotype there was a transient decrease, but by 2 h after the treatment the total ascorbate level had recovered and ratio of ascorbate to dehydroascorbate had increased 3-fold. After treatment, electrolyte leakage was faster in the S biotype, with the difference being more pronounced in the light. The differences between light and dark responses of the S and R biotypes suggested a light-dependent mechanism of resistance. Increasing levels of paraquat resulted in decreased variable fluorescence (F_v) values in both biotypes, with the F_v values of the R biotype exceeding those of the S biotype at all paraquat concentrations. The data indicate that paraquat does penetrate the chloroplast envelope of the R biotype. Paraquat was capable of diverting electrons from PSI [photosystem I] and exhibited phytotoxic action in the R biotype, albeit at a lower level than the S biotype. Ion leakage and fluorescence data are consistent with a mechanism of resistance that involves chloroplast photochemistry..

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